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| Author | Topic: oil cooling/heting of screw |
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michael wayne Senior Member Posts: 5 |
posted November 19, 2003 07:00 AM
  
could somebody help clear up some confusion i have understanding the reasons for using a screw oil heater. Oil Heater Con Air running at 120deg. We inherated the extruder and some profiles a short while ago, and began producing a variety of different producs without too many problems until we tried to run one product which looked indifferent from any other but proved to be very trying. ps very new to extrusion approx 12 months. ------------------ IP: Logged |
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zabielski Senior Member Posts: 251 |
posted November 19, 2003 07:46 AM
Screw cooling essentially removes excessive heat from the inside of the screw. Without this type of cooling, heater settings can easily over-ride due to adiabatic (frictional) heating from both the polymer as well as the mass of all metal's in the entire extrusion system - particularly from the mass of the screw shank and feed sections. In general, my experiance has been to use a fully bored (almost to the tip) cooling core (hole) with PVC's. As you already know, excessive het degrades PVC's, and the heat damage is accumlative. Some grades survive without screw cooling, but that's due to the stabilizer package, lubricants and other additives. You've simply come across with a very heat sensitive formulation that requires screw cooling. IP: Logged |
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michael wayne Senior Member Posts: 5 |
posted November 19, 2003 08:26 AM
Thanks for clearing that up. If this removes heat would i be able to use the oil heater on other products and would this effect surface finish and reduced power consumption etc. Or is it a case of trial and error. IP: Logged |
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Tom C Moderator Posts: 255 |
posted November 19, 2003 10:29 PM
Those who are familiar with this forum know that I beat this drum all of the time: Extrusion simulation allow you to predict and control the extrusion process and the results of process changes without having to resort to trial and error. While extrusion simulation software or services can be costly, the trial and error method can cost more. Tom Cunningham IP: Logged |
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Steve H Moderator Posts: 269 |
posted November 19, 2003 10:51 PM
There's not too many sleeps left till Xmas Tom, so I guess you can beat your drum, little drummer boy (pa-romp-pa-pom-pom)  Hi Michael, welcome to the extrusion forum. With PVC, degredation of material suffering excessive residence time in a stagnant zone out from the center of the screw tip is the reason for full lenght cooling. With other polymers, influencing the screws Co Efficient of friction and the feeding characteristics of the screw is the reason for cooling. Consider joining SPE's extrusion division and buying some books from their book store www.4spe.org Steve H [This message has been edited by Steve H (edited November 19, 2003).] IP: Logged |
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Tom C Moderator Posts: 255 |
posted November 20, 2003 08:12 PM
Gee Steve H., thanks for the Down Under; 1) Humour? Tom C [This message has been edited by Tom C (edited November 21, 2003).] IP: Logged |
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zabielski Senior Member Posts: 251 |
posted November 21, 2003 07:53 AM
Micheal Wayne: Look at this - this way: Keep doing what your doing and calculate your daily waste stream. Multiply this by the month. Then by the year. Get a qoute from Tom C, and compare the differences of $$. I doubt that he will charge you for the qoutation. What appears to be somewhat of a high professional Cunsultants fee - at first blush - may really be significantly lower than your waste costs. Don't forget to add in your downtime, as well as your costs for making the waste stream, re-handling, re-storage fee's, as well as reprocessing. My suggestion is to go to an expert who has all the right tools to use. My fear is this...you may not have the authority to authorize the expenditure, and you are afraid to bring this forward to your Management Team. If you do a simple $$ analysis on paper, as suggested, and put it all into a RETURN ON INVESTMENT (ROI) format on an annual basis, and show your Mangament Team the numbers, you will probably not only get the authorization, but perhaps some overlooked recognition that you deserve. While there is a multitude of professional Consultants out there, other than Tom C., I highly suggest you check out their credentials before hand. Unfortunately, there is a breed of unemployed people out there that automatically term themselves as "Consultant". Do yourself the favor of asking for their credentials as well as what tools they have on and to solve such problems. Tom C's expericanes and tools on hand are exellent from what he sent me to date. As previously stated, there are other Consultants to approach - but be careful. I've reviewed Tom C.'s resume, and abilities and this guy appears to have all the majic needed to resolve your problem. I myself am doing the same thing at this very moment (with hopes of finally meeting Tom C. face to face). IP: Logged |
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Steve H Moderator Posts: 269 |
posted November 21, 2003 01:00 PM
Mike The advice and suggestions given by both Ken and Tom are very sound, but from your comments, I think you need to spend some time(and money) getting up to speed with extrusion first. TAPPI's Polymer and Laminates division is another good source of extrusion info, check out their bookstore at www.tappi.org for their extrusion coating manual and blown film manual (yes I know you are doing profiles, but these two books have a lot of excellent general information on extrusion), SPE's Extrusion Solutions is another must have. Do a web search using google for extrusion, PVC extrusion etc etc and trawl for processing info, you'll get some good info that way. Study and document your process, after all it's your setup that is of concern to you. And what about the World Cup, is it going to be tears before bed time for the "Barmy Army"? Steve H Ps Tom C 1, 3,5 [This message has been edited by Steve H (edited November 21, 2003).] IP: Logged |
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2beeps Moderator Posts: 58 |
posted November 21, 2003 04:28 PM
All very good comments above re. the reasons for screw "cooling" I'll add a slightly different twist, albeit it's oriented towards PVC(rigid)Powder extrusion,whether single or twin screw----I see an oil-cored screw(oil temp.controlled via water heat exchanger-Sterelco unit)as a means to CONTROL screw temp.rather than just cooling.With oil-controlled screw temps,excess frictional heat of shear in material at the front end can be transferred towards the rear zones, to help promote powder fusion.The higher surface area of the screw (screws)compared to the barrel makes the screw a more efficient heat exchanger. Also, I've found that if screw oil temp. and barrel metering zone temp.are close to the same, a more balanced,smooth,and uniform viscosity melt is produced as material enters the adapter and die. Anyhow, just another viewpoint to muddy the waters IP: Logged |
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michael wayne Senior Member Posts: 5 |
posted November 24, 2003 10:35 AM
Thanks for all the healthy response. I am taken a back by all this knowledge. We are also processing TPE, TPV and polypro however i have not come across two many problems so far. One thing i am keen to learn about is PVC shear rate and melt fracture etc. Very happy with world cup result. ------------------ IP: Logged |
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